The river ice break-up season in Canada: variations in water levels and timing
Bibliographic record
Abstract
The break-up of river ice is an important component of the annual regime of rivers in the Northern Hemisphere and has been identified as a dominant control of annual peak water levels. Notwithstanding the environmental implications, the direct physical action of river ice and associated flooding during break-up can cause extensive damage to hydroelectric and transportation infrastructure resulting in substantial financial costs. With respect to climate change, these effects are expected to be exacerbated in the future. Presented here is a Canada-wide analysis of the trend (Mann-Kendall) in break-up water levels as well as quantitative timing related variables representative of the river ice break-up season. The data were extracted from original water level records supplemented with recent digital data at 136 Water Survey of Canada hydrometric stations and analyzed for the 1969-2006 period. In general, trends in water levels observed at the initiation of break-up (HB), as well as maximum water levels at break-up (HM) show declines ranging from 0.1-0.5 m/decade and 0.1-1.2 m/decade respectively. Simultaneously, the timing of both events has advanced by 1.4-4.7 days/decade for the former and 1.2-5.6 days/decade for the latter. Similarly, the timing of ‘last B date’ (last day of ice effects) has advanced by 1.5-8.6 days/decade. Assessed also are river ice break-up phases including break-up drive (t1), wash (t2) and duration (t3). With the exception of a few sites, the time (days) elapsed between break-up initiation and occurrence of peak water level (t1), shows no trend. In contrast, the majority of sites show an increase in the time elapsed between peak water level occurrence and ‘last B date’ (break-up wash, t2). Similar results are observed for the break-up duration (t3), suggesting that river ice break-up is occurring over a prolonged period of time. Overall, the river ice break-up season has experienced reduced break-up water levels, occurs earlier in the season and over an extended period of time.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".